1. Field of the Invention
The present invention relates to a polycrystalline silicon reactor which is used for producing polycrystalline silicon by the Siemens process.
Priority is claimed on Japanese Patent Application No. 2009-110149, filed Apr. 28, 2009, the content of which is incorporated herein by reference.
2. Description of the Related Art
The Siemens process is known as a producing process of the high-purity polycrystalline silicon that is raw-material of a semiconductor. The Siemens process is a producing process in which raw-material gas including a mixture of chlorosilane gas and hydrogen gas is in contact with heated silicon seed rods so that polycrystalline silicon may be deposited on the silicon seed rods by thermal decomposition and hydrogen reduction. As an apparatus for carrying out this process, a polycrystalline silicon reactor in which a plurality of silicon seed rods stand in a reactor is used.
When polycrystalline silicon is produced in the polycrystalline silicon reactor, chlorosilane polymer which is a by-product of the thermal decomposition and the hydrogen reduction condenses and sticks to a chilled inner-wall surface and a chilled floor surface of the reactor. In an exhaust gas of the reaction, unreacted raw-material gas, and hydrogen chloride gas are included with silicon powder and by-products such as silicon tetrachloride, polymer compound, and the like. The polymer compound such as chlorosilane polymer may ignite in air or may hydrolyze by moisture in the air, and hydrogen chloride may be generated. Therefore, before taking the deposited polycrystalline silicon out of the reactor, it is necessary to inactivate the polymer after the reactor is filled with inert gas.
As a process for inactivating the polymer, a process of heating and hydrolyzing accretion accreting to the inner-wall of the reactor by heating the reactor wall of the polycrystalline silicon reactor and introducing humidity controlled-gas into the reactor is described in Japanese Unexamined Patent Application, First Publication No. S56-114815 (Patent Document 1).
By hydrolyzing the polymer in the polycrystalline silicon reactor as abovementioned, silica, which is inert material, is generated. Therefore, the Patent Document 1 describes a process of removing and discharging the accretion of the inner-wall surface after dismounting a bell jar from a bottom plate and placing the bell jar on a table. On the other hand, since the bottom plate is provided with a plurality of protruded electrodes, nozzles for introducing or exhausting gas, and the like, it is a complex operation to clean the upper surface of the bottom plate. Therefore, it is required to clean the reactor efficiently.